Detergent tablets and method of producing same



United States Patent 3,331,780 DETERGENT TABLETS AND METHOD OF PRODUCING SAME Ewald H. Krusius, South River, N.J., assignor to FMC Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Nov. 26, B63, Ser. No. 326,239

6 Claims. (Cl. 252-135) This invention relates to a process for making heavyduty detergent tablets, and more specifically, to the production of detergent tablets which contain nonionic synthetic detergents and are sufiiciently strong to withstand breakage in a dry state but rapidly disintegrate when placed in heated wash water.

Heavy-duty, built, synthetic detergent tablets have become increasingly popular compared with liquid or powdered detergent compositions because of the more desirable handling characteristics which these tablets have. These tablets obviate the need for measuring cups used to dispense the powdered or liquid detergents required in domestic washing machines. They also eliminate spillage and the problem of storing bulky detergent containers. The manufacture of these heavy-duty nonionic detergent formulations is carried out by blending the components of the mix with water into a dry appearing, homogeneous, particulate, composition and pressing the composition into tablets so that they have sufiicient strength to resist breakage in handling and use, but are capable of rapid and uniform disintegration in wash water under conditions normally found in domestic washing machines.

In the makeup of detergent tablets the principal ingredients employed are a phosphate builder such as sodium tripolyphosphate, an anti-redeposition agent such as sodium carboxymethyl cellulose, a nonionic surface active agent such as nonyl phenol polyethoxy ethanol, and an anti-corrosion agent such as sodium silicate.

The formula also contains inert ingredients such as sodium sulfate; this is added as an extender to obtain the desired bulk density of the pelletizing mix, and results in a smoother and more solid appearing tablet. The most active cleaning components in the formulation are the phosphate builder and the nonionic surfactant. The antiredeposition agent is employed to prevent dirt from being redeposited on the washed clothes in the wash water. The anti-corrosion agent is added to prevent the alkaline detergent solution from attacking the metallic parts "of the washing machine.

A serious problem that has arisen during the manufacture of nonionic detergent tablets is that a given batch of detergent formulation does not yield tablets of uniform properties. That is, the tablets which are pressed from the formulation at the beginning of the tableting procedure have greater dry strength than do the tablets which are pressed from the final portions of the batch. The succeeding tablets in the batch become progressively weaker because of a loss in cohesive strength and tend to break and crumble when subjected to normal handling during packaging and shipment.

The lack of suflicient strength in the finished nonionic detergent tablets to withstand normal packaging and han dling is most objectionable to the consumer since one of the major benefits derived from using detergent tablets is avoiding the necessity of handling detergent powders or fines, thereby eliminating messy handling problems. This also poses serious difiiculty for the formulator, since the 3,331,780 Patented July 18, 1967 very same batch of formulation produced satisfactory tablets during one portion of the manufacturing procedure, but will not produce acceptably strong tablets during a succeeding portion of the manufacturing cycle.

It has been attempted to remedy this condition by increasing the tableting pressure during the tableting of succeeding portions of a batch of formulation. In this manner, acceptably strong tablets can be obtained from the entire batch. This has not proved successful in solving this problem because those tablets which are pressed under substantially higher pressures have required sub stantially increased dissolving times to dissolve the tablets in the wash water. This results in large pieces of the tablet not being utilized elfectively during portions of the washing cycle in conventional washing machines. Thus, the combination of a tablet sufiiciently strong to withstand breakage due to handling and packaging but which rapidly disintegrates in wash water is not obtained.

It is an object of the present invention to produce tablets having uniform and acceptable dry strengths so as to withstand normal handling and packaging, but which are capable of rapid disintegration in wash water.

It is a further object of the present invention to produce a formulation which will produce uniformly strong tablets wherein the time elapsed during tableting of the entire batch is not critical in determining the physical strength 'of the resultant tablets.

These and other objects will be apparent from the following disclosure.

I have now found that nonionic detergent tablets can be produced from a given batch of detergent formulation which have uniformly high strengths by pressing tablets from a particulate, normally water-soluble detergent formulation containing as essential ingredients a water-soluble nonionic synthetic organic detergent, a sodium polyphosphate and water, to which has been added a watersoluble aliphatic or cycloaliphatic polyol or a polyethylene glycol or polypropylene glycol in amounts of about 0.5% to about 10% by weight of the formulation.

It is believed that the inclusion 'of an additive such as the water-soluble aliphatic or cycloaliphatie polyol, or a polyethylene glycol, or a polypropylene glycol, prevents the hydratable ingredients of the formulations from taking up the water which is added to the formulation to improve its cohesive properties during tableting. In any event, the formulation retains its cohesive properties throughout the entire period during which it is pressed into tablets.

In the practice of this invention, a typical detergent formulationis made up as follows: The principal ingredient, sodium tripolyphosphate, is measured into the detergent formulation in amounts suflicient to constitute from about 35% to about 65% by weight of the detergent formulation. The most desirable range of sodium tripolyphosphate is from about 50% to about 65% by weight of the formulation. The sodium tripolyphosphate which is preferred has a low bulk density, i.e. 0.35 to about 0.6 g./cc., with about 0.45 to about 0.5 g./cc. being optimum. The method of manufacture of the sodium tripolyphosphate has not been found to materially affect the quality of the subsequent tablets.

The next added ingredient is the surface active agent (surfactant). This is normally added to the detergent formulation in amounts of from about 6% to about 14% by weight of the total formulation. Amounts below about 6% reduce the cleaning action of the detergent and should be avoided. Amounts over 14% should be avoided because the nonionic surfactant tends to exude or oil out of the detergent formulation when it is pressed into tablets. Within the range of about 6-14%, the nonionic surfactant gives effective washing action, and acts as an effective binder for the remainder of the detergent formulation Without oiling out of the pressed tablet.

The nonionic surface active agents useful in the present invention are non-soap synthetic detergents made up of a water solubilizing polyoxyethylene group in chemical combination with an organic hydrophobic compound. Among the hydrophobic compounds which can be used are polyoxypropylene, the reaction product of propylene oxide and ethylene diamine, aliphatic alcohols, etc. Examples of nonionic synthetic detergents useful in the present invention are condensation products of 6-30 moles of ethylene oxide with 1 mole of an alkyl phenol containing 6-12 carbon atoms in the alkyl group; condensation products of 6-30 moles of ethylene oxide with 1 m-ole of an aliphatic straight or branch chained alcohol containing 8-18 carbon atoms; condensation products of ethylene oxide and the reaction product of propylene oxide and ethylene diamine; nonyl phenol polyethoxy ethanol (commercially known as Triton N series); and

isooctyl phenol polyethoxy ethanol (commercially known as Triton X series). Another well known group of nonionic detergents is known under the trade name of the Pluronic series. These compounds are the reaction products obtained by condensing ethylene oxide with a hydrophobic base produced by the condensation of propylene oxide and propylene glycol, and have molecular weights onthe order of about 1800. The addition of polyoxyethylene radicals to the hydrophobic base increases the water solubility of the nonionic detergent and concurrently increases its foaming properties in aqueous solution in direct proportion to the mole ratio of polyoxyethylene radicals to the hydrophobic base. In general, a surfactant which has 7.5 moles of ethylene oxide per mole of alkyl (i.e. nonyl or iso-octyl) phenol is lowfoaming While one with a mole ratio of 10:1 foams moderately. The molecular weight of these nonionic synthetic detergents will range from as low as 800 up to about 11,000.

To the above mixture is added from about 3% to about by weight of sodium silicate having a Na O/SiO mole ratio of about 1:2 to about 1:3.2. The

optimum amounts of sodium silicate normally supply from about 3 to about 3.5 weight percent of SiO to the formulation. The sodium silicate which is selected for inclusion in the formulation must have a mole ratio of Na O/SiO' which permits the compound to dissolve rapidly but without increasing the pH of the detergent solution to levels which are unsafe for cloth fibers.

To the above mixture is added from about 0.5% to about 10% by weight of a water-soluble aliphatic or cycloaliphatic polyol, or a water-soluble polyethylene gly-' col or polypropylene glycol. The open-chained or acyclic polyols may be saturated or contain ethylenic linkages and may contain from 2 to 12 carbon atoms in the chain; they must have at least two alcohol groups attached to separate carbon atoms in the chain, and must be watersoluble so that they dissolve completely in the wash water. The polyols may be straight-chained or branch-chained. If desired, the compound may have an alcohol group attached to each carbon atom in the chain. Among the compounds which have been found effective are ethylene glycol, propylene glycol, glycerine, 2-methyl-2,4-pentane- -dio1, i-inositol and sucrose. The preferred polyol is propylene glycol which is effective in amounts as low as 0.5% by weight of the detergent formulation.

Water-soluble polyethylene glycols or water-soluble polypropylene glycols useful in the present invention are those products produced by the condensation of ethylene glycol molecules or propylene glycol molecules to form high molecular Weight ethers having terminal hydroxy groups. The polyethylene glycol compounds may range from diethylene glycol to those having molecular weights as high as about 6,000. Normally, polyethylene glycols having molecular weights up to about 800 are liquid and are completely soluble in water. As the molecular weight of the polyethylene glycols increases, they become solid commencing from molecular weights of about 1,000 to about 6,000. These compounds have decreased solubilities in water as the molecular weight increases; nevertheless, these compounds, up to molecular weights of about 6,000, have been found to have sufficient water solubility to be useful in the present invention. The poly propylene glycol compounds useful in the present invention may range from dipropylene glycol to polypropylene glycols having a molecular weight of about 2,000. These are normally liquids at room temperature and are readily soluble in water.

Sodium sulfate is added to the above mixture to make up the remaining major proportion of the formulation. The sodium sulfate is an inert filler which is added to control the bulk density of the tableting mixture and to improve the surface appearance of the tablets by giving a'smoother and more compact appearance. In addition, there is also added small amounts of auxiliary compounds such as sodium carboxymethyl cellulose (in amounts of from about 02-15%), foam stabilizers such as lauroyl diethanolamide, tarnish inhibitors, fluorescent brighteners, perfumes, bacteriostats, coloring matter, etc.

To the above formulation is added sufficient water to render the ingredients adherent when they are pressed into a tablet. The amount of Water added may range from 110%. If desired, the water may be added wholly or in part as the vehicle for the sodium silicate by adding an aqueous colloidal dispersion of the sodium silicate. The resultant water-soluble detergent formulation should have a bulk density in the range of about 0.5 to about 0.85 g./cc. The mixture is then pressed into tablets having a density of from about 0.8 to about 1.3 g./cc.

During the pressing operation, the amounts of pressure necessary to press the tablets in the dies indicates the cohesive properties of the forrnulati-on. It is believed that when the hydratable ingredients of the formulation commence taking up the added water, as water of hydration,

the cohesive force of the formulation decreases and the mixed formulation remains standing before being tableted.

In normal commercial operations, the tableting-machine is set to press a batchof formulation to a predetermined volume to produce uniformly sized tablets. If V the amount of pressure which is required to press the tablet increases, the tableting apparatus nevertheless continues to press to the preset volume. As a result, succeeding tablets pressed under higher pressure will be pressed more tightly and therefore will dissolve more slowly.

In tableting the instant detergent formulation, it has been found that small portions of the mixture do not adhere to the dies, nor is there any capping during the pressing of these formulations. The term capping refers to the internal separation of the tablet into two pieces because of the adherence of these pieces to each of the dies. In general, the use of standard dies is-eminently satisfactory without special provisions for rotation of the dies during the pressing operation.

The resulting pressed tablets may be subjected, if desired, to a steaming in order to hydrate a surface layer of hydratable components, e.g. sodium tripolyphosphate ing the surface density and the cohesive force between the particles, and prevents chalking.

In addition to their primary purpose of preventing the drying out of the formulation, the added polyols impart desirable properties to the detergent formulation. Initially, the preferred polyol, namely propylene glycol, functions as an excipient and permits clean separation of the tablets from the mold or dies. This is most desirable, since in many tableting procedures, a mold release spray cycle is necessary to spray the mold with special excipients in order to get clean separations of the tablets from the dies. The use of the propylene glycol completely eliminates the need for such a special cycle.

The following examples are given to illustrate the invention and are not deemed to be limiting thereof.

Example 1 Run A.--The following detergent formulations were mixed in a Kitchen-Aid planetary mixer (Model 4-C, Hobart Manufacturing Company, Troy, Ohio), until a homogeneous mixture was obtained. The solid ingredients were mixed together first, then the liquids were slowly added while mixing was continued.

1 Bulk density 0.52, screening analysis: 99+%, 30 mesh; 20%, -70 mesh; 2.6+, 100 mesh.

2 Isooctyl phenol polyethoxy ethanol containing 7-8 moles of ethylene oxide per mole of isooctyl phenol.

3 Aqueous mixture containing 37.1 weight'percent of sodium silicate having a NazO/SiO mole ratio oi1:2.5; the liquid mixture has a specific gravity ol1.408.

The formulations having bulk densities as listed in Table I were pressed in a Carver press to form tablets weighing 29 g., having a thickness of 16.5 mm. and a density of 1.35 g./cc. The resultant tablets were steamed for 120 seconds and were allowed to age by open air exposure. The tablets were pressed from the formulation over a period of 210 minutes and the pressure required to press the tablets to constant volume was recorded and is listed in Table I. In addition, the dissolving rate of the tablets was determined by adding the tablets to a 16-gallon Kenmore transparent-sided washer containing wash Water at 120 F. The dissolution time is the time required for complete dissolution of the tablet.

TABLE I Tableting (gauge) Pressure (lbs.) Formulation Bulk Density of Formulation Dissolution Time (sec) of t blets ressed after 180 n 1in 197 218 154 86 57 Run. B.By way of comparison, a detergent formulation was made up which was free of a polyol additive. This formulation was made up in the same manner as the previous formulations containing the following in- 5 gredients:

Percent Sodium tripolyphosphate 1 58 Sodium carboxymethyl cellulose 0.5 Sodium sulfate 5.5

10 TIllOH X-1142 12 Star silicate 3 14 Water 10 -See footnote in column 5. 2 See footnote in column 5. 3 See footnote in column 5.

The formulations were pressed in a Carver press in the same manner as reported previously. The pressure necessary to obtain constant volumes was determined immediately after the mix was prepared and after the mix was allowed to stand for 180 minutes. Thereafter, the tablets were tested for dissolution time as set forth above. The results of these tests are given in Table II.

Example 1, Run A, Formulation 1, was made up using i-inositol (1,2,3,4,5,6-cyclohexanehexol) in place of glycerine and tested as set forth in Example 1. The results obtained were of the same order as when glycerine was employed in the formulation.

Example 3 Run A.The following detergent formulation was mixed in a Kitchen-Aid rotary mixer (Model 4C, Hobart Manufacturing Company, Troy, New York), until a homogeneous mixture was obtained. The solid ingredients were mixed together first, then the liquids were slowly added while mixing was continued.

Formulation (percent) Ingredient Sodium tripolyphosphate 1 58 58 Sodium earboxymethylcellulose 0. 5 0. 5 Sodium sulfate (anhydrous) 13. 5 13. 5

Triton X-1l4 2 12 12 Star Silicate 3 14 14 Diethylene glycol 2 Polypropylene glycol (M-W- 1955) 2 1 See footnote in column 5. 2 See footnote in column 5.

60 3 See footnote in column 5.

These formulations were then pressed in a Carver press to form detergent tablets. A constant pressure of 1600 pounds was used to compress identical amounts of the formulation. The resulting tablets were steamed for seconds and were allowed to age by open air exposure. The tablets were pressed from the formulation over a period of minutes and the thickness of the tablet was recorded and is listed in Table III. In addition, the dissolving rate of the tablets was determined by adding the tablets to a 16-ga1lon Kenmore transparent-sided Washer containing wash water at 120 F. The dissolution time is the time required for the complete dissolution of the 7 tablet.

Run B.By way of comparison a detergent formulation was made up which was free of polyol additive. This formulation was made up in substantially the same manner as the previous formulations and contained the following ingredients.

Ingredient: Percent Sodium tripolyphosphate 1 52.2 Sodium sulfate (anhydrous) 12.3 Sodium carbonate 1.9 Triton X-ll4 14.25 Sodium carboxymethyl cellulose 1.0 Star silicate 3 12.85 Water 5.5

1 See footnote in column 5.

2 See footnote in column 5.

3 See fo tnote in column 5. One portion of the formulation was pressed in a Carver press at a constant pressure of 1600 pounds; the other portion was pressed in the Carver press to a constant volume. The force necessary to compress identical amounts of the formulation to constant volume, as well as the volume obtained when identical amounts of the formulation were pressed under constant pressure, were determined immediately after the mix was prepared and also after the mix was allowed to stand for periods up to 120 minutes. These results are reported in Table IV along with the dissolution time for tablets pressed after 120 minutes.

TABLE IV Pressed under Pressed to a 1,600 lbs. Tablet Constant Vol- Thickness ume; Force (mm.) applied (lbs) Time (minutes)- Dissolution time of tablets pressed after 120 minutes, sec 144 372 In the preceding examples, the formulations were compressed into the tablets of a constant volume, as is common in industrial tablet production, after various lengths of time up to about 2 hrs. in order to show the increase in pressure resulting from standing prior to pressing of the formulations. A 2-hour or longer pressing period for asingle batch of detergent feed is common in industrial practice. As shown in Example 1, Run A, the addition of the polyol in place of some water allows the formulation to be compressed to constant volume without a serious increase in pressure throughout the 3 /2-hour pressing operation. In the absence of the polyol, the formulation requires substantially increased pressures to compress it 8 to constant volume after standing for 3 hours as shown in Example 1, Run B. These high pressures result in undesirably long dissolution times (see Table II).

When the formulations which do not contain the polyol additive were pressed at constant pressure (see Example 3), that portion of the formulation which remained standing before being pressed (during which it is believed that partial hydration occurs) was not fully compressed to the desired volume; the applied pressure is not suflicient to completely press the formulation into tablets of the desired size. The results are oversized, incompletely pressed 7 tablets, having poor strength.

Pursuant to the requirements of the patent statutes,

the principle of this invention has been explained and exemplified in a manner so that it can be readily practiced by those skilled in the art, such exemplification including what is considered to represent the best embodiment of the invention. However, it should be clearly understood that, within the scope of the appended claims, the invention may be practiced by those skilled in the art, and having the benefit of this disclosure, otherwise than as specifically described and exemplified herein.

What is claimed'is 1' 1. Process for producing detergent tablets from a detergent formulation which disintegrate rapidly when placed in heated wash water and which have uniformly'high strengths comprising pressing tablets from a detergent formulation comprising 35-65% by weight sodium tripolyphosphate, 3-15% by weight sodium silicate having a mole ratio of Na O/SiO of 1:2 to 1:3.2, 615% by Weight of a water-soluble nonionic synthetic organic detergent containing a water solubilizing polyoxyethylene group, 1-10% by weight water, 0.5l0% by weight of a V Water-soluble polyol selected from the group consisting of alkyl and cycloalkyl polyols having from 2-12 carbon atoms, polyethylene glycol having molecular weights up to 6000 and polypropylene glycol having molecular Weights up to 2000, and the balance of the formulation being sodium sulfate.

2. Process of claim 1 wherein said detergent formula tion contains 0.2-1.5% by weight of sodium carboxysity of about 1.02 g./ cc.

References .Cited UNITED STATES PATENTS 2,643,229 6/1953 Walters 252-161 2,875,155 2/1959 Miles 252-138 2,972,583 2/1961 Hewitt 252-138 X 3,081,267 3/1963 Laskey 252- 3,210,287 10/1965 Kelly et a1. 252-135 X 3,231,506 1/1966 Schulerud 252-138 LEON D. ROSDOL, Primary Examiner. ALBERT T. MEYERS, Examiner.

I. GLUCK, Assistant Examiner, 

1. PROCESS FOR PRODUCING DETERGENT TABLETS FROM A DETERGENT FORMULATION WHICH DISINTEGRATE RAPIDLY WHEN PLACED IN HEATED WASH WATER AND WHICH HAVE UNIFORMLY HIGH STRENGTHS COMPRISING PRESSING TABLETS FROM A DETERGENT FROMULATION COMPRISING 35-65% BY WEIGHT SODIUM TRIPOLYPHOSPHATE, 3-15% BY WEIGHT SODIUM SILICATE HAVING A MOLE RATIO OF NA2O/SIO2 OF 1:2 TO 1:3.2, 6-15% BY WEIGHT OF A WATER-SOLUBLE NONIONIC SYNTHETIC ORGANIC DETERGENT CONTAINING A WATER SOLUBILIZING POLYOXYETHYLENT GROUP, 1-10% BY WEIGHT WATER, 0.5-10% BY WEIGHT OF A WATER-SOLUBLE POLYOL SELECTED FROM THE GROUP CONSISTING OF ALKYL AND CYCLOALKYL POLYOLS HAVING FROM 2-12 CARBON ATOMS, POLYETHYLENE GLYCOL HAVING MOLECULAR WEIGHTS UP TO 6000 AND POLYPROPYLENE GLYCOL HAVING MOLECULAR WEIGHT UP TO 2000, AND THE BALANCE OF THE FORMULATION BEING SODIUM SULFATE. 